The present invention relates to apparatus for scanning a sheet bearing contrasting scannable written or printed information (hereinafter sometimes simply referred to as a xe2x80x9csheetxe2x80x9d), and more particularly, to means and a process for keeping a reference scanning surface of the device clean.
Conventional designs of apparatus such as facsimile transmission units (i.e., a xe2x80x9cFAXxe2x80x9d) and document or page readers, for scanning sheets (e.g., scannable matter) bearing contrasting written or printed matter, generally include a passage through which scannable matter is transported by means of transfer rolls, past a scanning plate with a reference scanning surface positioned over the passage while a light source projects a light beam upon either the reference scanning surface or on any intervening sheet of scannable matter. The light beam reflected from the reference scanning surface is delivered to the photoelectric conversion device and is converted into an electric signal that is stored in a memory device as a reference value. Scanned image information created by reflection of the light beam from a moving sheet is converted into an electric signal and compared with the reference value stored in the memory device to determine brightness of the image information in relation to the reference value.
In such a conventional apparatus however, the reference scanning surface is coated with paint having a reference color, for example, a white color, which is similar to the color of a sheet of scannable matter to be scanned. The paint with the reference color is typically produced by mixing many colors under a specific surrounding condition. Therefore, it is very difficult to always make the same reference color under different color mixing conditions. Moreover, the sheet itself varies in composition and color, depending upon the paper mill, process and esthetic considerations attendant upon its manufacture. Hence, it is very difficult to effectively control the scanning quality of the apparatus. Moreover, when a reference scanning surface that has been contaminated through prolonged use, and is cleaned by using a cleanser, the coated paint deteriorates or even peels off from the underlying surface of the apparatus.
It is therefore an object of the present invention to provide an improved apparatus and process for scanning sheets bearing information.
It is another object to provide means for easily enabling maintenance of the cleanliness of a reference scanning surface.
It is yet another object to provide an improved reference surface in a device for scanning media bearing contrasting written or printed information.
It is still another object to provide an easily replaceable reference surface in a device for scanning media bearing contrasting written or printed information.
It is a further object to provide a reference surface enabling quick and inexpensive restoration of its surface characteristics in a device for scanning media bearing contrasting written or printed information.
These and other object can be achieved according to the present invention, with an apparatus for scanning media bearing written or printed information, using apparatus that has passages through which the written or printed sheet is transported, a scanning plate with a reference scanning surface positioned over the passage and exposed to a beam of light, and a removable scanning surface having a reference color positioned between the beam of light and the reference scanning surface. The removable scanning surface may be an adhesive, scanning tape that is readily detachable from the reference scanning surface so as to enable its replacement with a fresh one when the adhesive scanning tape is discolored or contaminated from prolonged use.
The present invention will be more specifically described with reference to the drawings attached only by of example.